The present invention relates to a skin electrode construction, and also to a transdermal drug delivery device including such a construction. The invention is particularly applicable to skin electrode constructions for delivering drugs by iontophoresis, and is therefore described below with respect to this application.
Iontophoresis is the process of moving ions into surface tissues with the aid of an electric current. Although this process has long been known, its use for the transdermal delivery of a drug has only recently become of great interest, and many such devices are described in the literature. However, one of the serious limitations in the use of this technique, particularly for delivering drugs at an optimum rate, is the tendency of the device to irritate or burn the recipient's skin because of the heat generated by the iontophoresis electrodes.
Tapper U.S. Pat. No. 4,164,226 discloses an electrode structure to provide protection against skin burns, particularly during transdermal drug delivery by iontophoresis, by covering the face of the skin electrode, normally to be in contact with the subject's skin, with a felt-like material, preferably moistened by a liquid. However, such a device is of very limited application since it cannot be rejuvenated nor can its moisture content be controlled.